According to the World Health Organization, to stop or eventually reverse the rise in obesity prevalence, broad, population-based approaches are needed. Obesity prevention can be achieved by promoting a healthy diet and a physically active lifestyle. In response to this Request for Application, a partnership with Eastman Kodak Co., the major employer in Rochester, NY, has been developed to test a worksite intervention for obesity prevention. The overall goal of this proposal is to design a comprehensive nutrition and physical activity strategy based on participatory research involving the three levels of the epidemiologic triad (host, environment, and agent) to promote a healthy lifestyle and, as a consequence, to stop the shift of the population body mass index curve to the right. In order to achieve the goal of this proposal, the specific aims are: (1) To gain a broad understanding of the social/cultural role of food and physical activity among workers as well as to elicit workers' perspectives on innovative interventions that are socially feasible and culturally acceptable; (2) To perform a Nested Pretest-Posttest Control Group Cross-Sectional design to test healthy lifestyle promotion interventions addressing portion control, healthy nutrition, and sedentarism. Six pairs of worksites will be randomized to intervention and control conditions. Two cross-sectional samples of employees within worksites will be measured at baseline and at the end of the intervention. The pattern of the outcome measures will be observed by following a cohort of employees overtime.; (3) To perform Process and Outcome Evaluation to assess the implementation of strategies and intermediate outcomes; (4) To identify the economic benefits of the workplace intervention by using a cost-effectiveness approach from the societal and business perspective; and (5) To develop methods for fast-track information dissemination across the scientific and occupational health disciplines. The strategies and tools developed will have a potential impact on 20,000 employees in the Rochester, NY area and 60,000 worldwide.